1. Technical Field
The invention relates generally to behavior analysis of animal objects. More particularly, one aspect of the invention is directed to monitoring and characterization of behaviors under specific behavioral paradigm experiments, including home cage behavior paradigms, locomotion or open field paradigm experiment, object recognition paradigm experiments, variety of maze paradigm experiments, water maze paradigm experiments, freezing paradigm experiments for conditioned fear, for an animal, for example, a mouse or a rat, using video analysis from a top view image or side view image, or the integration of both views.
2. Background Art
Animals, for example mice or rats, are used extensively as human models in the research of drug development; genetic functions; toxicology research; understanding and treatment of diseases; and other research applications. Despite the differing lifestyles of humans and animals, for example mice, their extensive genetic and neuroanatomical homologies give rise to a wide variety of behavioral processes that are widely conserved between species. Exploration of these shared brain functions will shed light on fundamental elements of human behavioral regulation. Therefore, many behavioral test experiments have been designed on animals like mice and rats to explore their behaviors. These experiments include, but not limited to, home cage behaviors, open field locomotion experiments, object recognition experiments, a variety of maze experiments, water maze experiments, and freezing experiments for conditioned fear.
Animal's home cage activity patterns are important examination item on the general health list of animals, such as mice and rats. It provides many important indications of whether the animal's health status is normal or abnormal. Home cage behaviors are best observed by videotaping several 24-hour periods in the animal housing facility, and subsequent scoring of the videotape by two independent observers. However, this observation has rarely been done until our inventions came into play, due to the instability in long term human observation, the time consumed, and the huge costs associated with the observation.
A conventional method for measuring animal's spatial navigation learning and memory is the water maze task, in which the animal swims to find a hidden platform, using visual cues to locate the platform. This task is based on the principle that rodents are highly motivated to escape from a water environment by the quickest, most direct route. (Wenk, 1997) Experiment sessions are usually videotaped, and human observation of videotapes or automated software is used, depending on the parameters required for observing the session.
Variations of popular methods for measuring animal's spatial navigation learning and memory include other maze designs, such as T-maze, Y-maze, and radial arm maze. In all cases, the task requires the animal to choose specific arm(s) of the maze to receive a food or water reinforcement or to avoid a footshock. The shapes of the arms make the differences among T-maze, Y-maze, and radial arm maze. The animal is habituated and then shaped to obtain the reinforcer. Variations of popular methods for measuring animal's anxiety-related behaviors include elevated plus maze, zero maze, etc. Measuring anxiety using elevated plus maze or zero maze rests on the naturalistic conflict between the tendency of animal such as mice to explore a novel environment and the aversive properties of a brightly lit, open area. Elevated plus maze is elevated from the ground about a meter with four (4) arms, two well lit and two closed and dark. Animals such as mice or rats prefer the closed arms but will venture out into the open arms, with a start box in the center. The zero maze is similar, but has annulus of an elevated circular runway, with areas brightly lit alternate with dark, covered areas. We group all of these experiments under “maze”. Though the theory and operations and training may be different among these mazes, the observation and measurement is basically similar, i.e., the measurement of animal staying in each arm or arena, closed or open. Experiment session is usually videotaped, and human observation of videotapes or automates software is used, depending on the parameters required for observing the session.
Another method to measure animal's such as mice or rats, capability in spatial learning and memory and their tendency of exploration is the experiment of object recognition, or novelty seeking. Its objective is to measure reduced time spent exploring a novel object that replaced a training object after a specified retention time. Objects of different shapes and colors are placed in an open field, and animal is place in the field. The number of times the animal sniffs at each object, and the duration of each sniffing are measured to show the animal's tendency to explore. Objects are replaced with new objects from time to time. The experiment session is videotaped, and human observation of videotapes is used to measure those parameters.
The most standardized general measure of motor function is spontaneous activity in the open field. Square, rectangular, and circular equipment is presently in common use. Sizes of open fields range from centimeters to several meters. Scoring of videotaped session allows quantization of animal's spontaneous activity. Automated open fields now routinely used in behavioral neuroscience laboratories are equipped with either photocell beams or video tracking and computer software. Both types of automated systems calculate a useful range of basic locomotor parameters.
Freezing test is designed for cued and contextual fear conditioning, which is among the most intuitive memory paradigms. Freezing is a common response feared situation in many species, and is defined as no movements other than respiration. Conditioning training consists of placing the mouse in the chamber and exposing to a mild footshock paired with auditory cue. Freezing is measured when the trained mouse is placed back in the same chamber for training with auditory cue, and scored for bouts of freezing behavior. Human observation of videotapes of the session is used for this scoring, which is inaccurate and expensive. Automated system using mechanical principle exists to help real-time scoring of freezing. However, the precision of such a mechanical system need to be further improved.
As discussed, all these apparatus and experiments use, in many cases, human observation of videotapes of the experiment sessions, resulting in inaccuracy, subjectivity, labor-intensive, and thus expensive experiments. Some automating software provides rudimentary and basic parameters, relying on tracking animal as a point in space, generating experiment results that are inaccurate and can not meet the demands for advanced features. Besides, each system software module works for only a specific experiment, resulting in potential discrepancy in the results across different systems due to differences in software algorithms used.
All the observations of these behavioral experiments use video to record experiment processes and rely human observations. This introduces the opportunity to utilize the latest technologies development in computer vision, image processing, and digital video processing to automate the processes and achieve better results, high throughput screening, and lower costs. Many of these experiments are conducted with observations performed from top view, that is, observation of the experiments from above the apparatus is used to obtain needed parameters. This also provides an opportunity to unify the approaches to observe and analyze these experiments' results.